| 青藏高原东缘岩石圈结构对现今地表垂向运动影响的数值分析 |
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| 引用本文： | 庞亚瑾,程惠红,张怀,石耀霖.青藏高原东缘岩石圈结构对现今地表垂向运动影响的数值分析[J].地球物理学报,2019,62(4):1256-1267. |
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| 作者姓名： | 庞亚瑾 程惠红 张怀 石耀霖 |
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| 作者单位： | 1. 中国地震局第一监测中心, 天津 300180;2. 中国科学院计算地球动力学重点实验室, 中国科学院大学, 北京 100049 |
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| 基金项目： | 国家自然科学基金（41804091），地震科技星火计划（XH19063Y），国家重点研发计划（2016YFC0600504）和中国地震局震情跟踪定向工作任务（2018010202）联合资助. |
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| 摘 要： | 参考青藏高原东缘松潘-甘孜地块至四川盆地陡变地形起伏和地壳密度结构的横向差异，本文建立了二维牛顿黏性流体有限元模型，计算分析构造加载、陡变地形和重力效应控制下青藏高原东缘岩石圈变形特征，探讨横向不均匀的地壳密度结构、陡变地形和岩石圈流变性质对区域现今垂向运动的影响.计算结果显示：在构造加载作用下，松潘-甘孜地块至四川盆地地表抬升微弱.区域横向不均匀的地壳密度结构驱使松潘-甘孜地块地壳整体抬升，速率高达2 mm·a-1，四川盆地整体下沉，速率约1 mm·a-1，与龙门山两侧现今观测到的地表垂向变形模式相近.龙门山地区陡变地形驱使柔性地壳流动，调整区域地壳局部变形；岩石圈流变结构影响重力驱动作用下的模型变形量值和岩石圈变形耦合程度，松潘-甘孜地块较低的中地壳黏滞系数引起上、下地壳的变形解耦；模型较高的岩石圈地幔黏滞系数使重力驱动作用下区域垂向变形量降低.因此，青藏高原东缘地壳密度结构差异、地形起伏和岩石圈流变性质是现今区域垂向变形的重要动力学控制因素.
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| 关 键 词： | 青藏高原东缘 垂向运动 陡变地形 地壳密度结构 有限元模拟 |
| 收稿时间： | 2018-09-15 |
Numerical analysis of the influence of lithospheric structure on surface vertical movements in Eastern Tibet |
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| PANG YaJin,CHENG HuiHong,ZHANG Huai,SHI YaoLin.Numerical analysis of the influence of lithospheric structure on surface vertical movements in Eastern Tibet[J].Chinese Journal of Geophysics,2019,62(4):1256-1267. |
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| Authors: | PANG YaJin CHENG HuiHong ZHANG Huai SHI YaoLin |
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| Institution: | 1. The First Monitoring and Application Center, China Earthquake Administration, Tianjin 300180, China;2. Key Laboratory of Computational Geodynamics, Chinese Academy of Sciences, Beijing 100049, China |
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| Abstract: | Based on the steep topography and pronounced contrast in crustal densities from Songpan-Garzê block to Sichuan basin in Eastern Tibet, we set up a 2-D finite element model using the Newton viscous constitutive equations, to quantitatively analyze the lithospheric deformation in Eastern Tibet driven by tectonic loading, steep topographic relief and regional gravity. We further discuss the influences of the lateral heterogeneity in crustal density, topography relief and lithospheric rheology on regional vertical movements. The numerical results show that:The tectonic loading induces slight vertical uplift from Songpan-Garzê block to Sichuan basin, while the gravity adjustment due to lateral heterogeneity of crustal density leads to whole-scale uplift up to 2 mm·a-1 in Songpan-Garzê block, and surface subsidence of~1 mm·a-1 in Sichuan basin, with the deforming pattern similar to the observed vertical movements. The steep topography in Longmenshan region induces pronounced ductile crustal flow, and adjusts the local crustal deformation. The lithospheric rheology affects the regional deformation and coupling extent between each layer of the lithosphere, with lower viscosity of middle crust leading to decoupling deformation in the Songpan-Garzê block, and higher viscosity of the lithospheric mantle inducing less vertical movements driven by regional gravity effect. Therefore, the lateral heterogeneity of crustal density, topography relief and rheology of the lithosphere are the significant controlling factors for regional vertical movements in Eastern Tibet. |
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| Keywords: | Eastern Tibet Vertical movements Steep topography Crustal density Finite element modeling |
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